This invention relates to boilers and more particularly to high efficiency water boilers for use in hydronic heating systems for residential application and the like.
There have been many boilers devised over the years for heating water used in residential hydronic heating systems. In general, each of these boilers comprises a housing which contains an insulated combustion chamber. The combustion chamber contains a burner unit which is connected to a fuel source such as pressurized gas. Combustion of a mixture of gas and air in the chamber causes the radiation of heat outwardly from the burner unit and the generation of convection currents of hot combustion products which rise toward an exhaust outlet at the top of the combustion chamber. In passing to the exhaust outlet the convection currents of hot combustion products flow past a heat exchanger which may comprise a series of thin copper tubes lying in a horizontal plane and carrying the water to be heated. The tubes conduct the heat acquired by radiation and conduction to the water flowing through the tubes. Headers are provided at both ends of the tubes to route the water from an inlet port, through the tubes and then to an outlet port.
While the use of horizontally disposed copper tubes as a heat exchanger provides rapid water heating, this configuration possesses several disadvantages. For example, the hot air rising in the combustion chamber transfers significant amounts of heat to the side walls of the housing. Accordingly, all of the walls of the housing must be insulated, typically by refractory material. The required thick sidewall insulation results in boilers which are both large and heavy. In addition, the heat transferred to the sidewalls by convection and radiation does not contribute to increased water temperature, resulting in a loss of boiler efficiency.
Accordingly, it is an object of this invention to provide a new and improved boiler.
It is another object of this invention to provide a high efficiency boiler which is smaller and lighter in weight than prior art boilers having similar heating capacity.
It is yet another object of this invention to provide a boiler which employs both horizontal and vertical heat exchangers.